Boom control in power cranes



Nov. 24', 1959 w. c. HOLMES BOOM CONTROL IN POWER CRANES 3 Sheets-Sheet 1 Filed Nov. 14, 1955 Nov. 24, 1959 W. C. HOLMES BOOM CONTROL IN POWER CRANES I Filed Nov. 14, 1955 5 Sheets-Sheet 2 WWW JZZZL Arron/WE) W. C. HOLMES BOOM CONTROL IN POWER CRANE-S Nov. 24, 1959 3 Sheets-Sheet 3 Filed NOV. 14, 1955 INVENTOR. Ma BY United States Patent BOOM CONTROL IN POWER CRANES William C. Holmes, River Rouge, Mich.

Application November 14, 1955, Serial No. 546,398

1 Claim. (Cl. 254145) My invention pertains to means of controlling the lowering of a boom, particularly when the boom carries a heavy load. The invention is intended to be used on the type of power cranes in which it is possible to regulate the unwinding of the boom-operating cable from its drum by coupling the drum to the engine of the crane. Ordinarily the lowering of the boom is effected by means of a single lever which is operated manually and by means of which a satisfactory control of speed in the lowering of the load may be attained. When heavy loads are to be carried by the boom, and when the loads have to be lowered carefully to avoid damaging the load or injuring the workers in proximity of the place where the load is to be lowered, it was necessary to couple the drum to the engine of the crane and to control the speed of the lowering of the load by the speed of the engine. In order to do so, the operator of the crane had to actuate a special lever serving that particular purpose. As under the stress of work or because of a temporary diversion of his attention the operator was likely to forget to actuate said lever in order to regulate the speed of the lowering of the boom by said engine, I have devised means whereby the coupling of the engine to the cable drum will be effected automatically, thus rendering the matter independent of the operators attention or lack thereof.

I shall now describe my improvement with reference to the accompanying drawings in which:

Fig. l is a diagrammatic presentation of a power crane of the kind in which my device is to be employed;

Fig. 2 is a side elevational view of the mechanism controlling the operation of the boom of the crane, the view including my device;

Fig. 3 is a rear view of a lever controlling the raising and the lowering of the boom, the view being taken on line 3-3 of Fig. 2;

Fig. 4 is a sectional view on line 4-4 of Fig. 3;

Fig. 5 is a side elevational view of a locking mechanism for the lever shown in Fig. 3;

Fig. 6 is a top elevational view of my device, the view being taken on line 6--6 of Fig. 2;

Fig. 7 is a top elevational View of the elements shown in Fig. 6, but in different operative positions;

Fig. 8 is a sectional view on line 8-8 of Fig. 6;

Fig. 9 is a sectional view on line 9-9 of Fig. 6;

Fig. 10 is a sectional view on line 1010 of Fig. 2;

Fig. 11 is a sectional view on line 1111 of Fig. 2;

Fig. 12 is a partly schematic side elevational view of a brake mechanism shown in combination with the cable drum and means to control the rotation thereof.

Similar numerals refer to similar parts throughout the several views.

The principal elements of the power crane are shown in Fig. l in which the crawler-type traction gear is marked 10, the cab mounted thereon is marked 11, and the boom is identified by numeral 12, while the cable by means of which the boom may be raised or lowered is marked 13. Numeral 14 identifies a bucket.

I the ratchet wheel, preventing its rotation.

Prior to the description of my device, I will refer to the standard mechanism for raising and lowering the boom. As the mechanism is well known, minor details of its construction will be only alluded to or entirely omitted.

On reference to Fig. 2, it will be noted that boom 12 is pivotally mounted at its lower end, as shown at 15, within bracket means 16 at the front portion of the turntable 17 which carries the mechanism for the operation of the crane as a whole. It is at the upper end of the boom thatsaid cable 13 is attached thereto. The cable 1 passes over a pulley 18 at the upper end of a stationary beam 18a mounted on turntable 17 and is wound upon a drum 19 also mounted upon said turntable.

The rotation of the drum is controlled by means of a gear wheel 20 which is co-axially mounted with the drum on a shaft 21. The gear wheel is in mesh with an idler 22, and by means of said idler is in engagement with a pinion mounted upon a shaft known as a swing shaft 100, shown in dotted lines in Fig. 2. Mounted on the shaft and keyed thereto is a brake wheel 24, and encircling the wheel is a brake band 25 which at one end is anchored to a stationary member 27 mounted upon the upper surface of the turntable. The other end of the brake band is connected to a horizontal rod 28. A spring 29 coiled about the rod and bearing at one end against a stationary member 29a keeps the band in a tight frictional engagement with the rim portion of the brake wheel 24. A ratchet wheel 30, mounted upon the same shaft which carries said brakewheel, is controlled by a shoulder 79 upon a horizontal bar 7 6 to which I shall refer again.

The shoulder, serving as a pawl, is in engagementwith When the boom is to be lowered, it is first necessary for the operator to disengage the pawl from. the ratchet. Next, the brake band 25 upon the brake wheel 24 has to be loosened. This is effected by meanso-f a lever 32 which is one of the levers in front of the operator. The lever is mounted pivotally, by means of a pin 33, in a bracket 34 upon the turntable 17. The .lOWEI' end of the lever, below said pin 33, is connected pi'votally, as shown at 35,'to one end of a horizontal link 36 which at its other end is pivotally connected to a bell crank 38, as shown at 37 in Fig. 11.

Mounted upon the crank, at its mid-portion, as shown in Fig. 12, is a vertical member 39, best called abrakerelease lever, the-lever being pivoted upon a pin 40 and inclinding a short arm 41 extending above said pin and being in engagement with said rod 28. The arm serves to impart a longitudinal movement to the rod against the tension of said spring 29, and, thus, to loosen the brake band 25. It must be added here that the crank 38 operates a vertical clutch lever 42 which is pivoted midway its length, as shown at 43-, and which includes a forked upper end 44- connected to-a clutch 45 on one end of theswing shaft. 1

When the boom is to be raised, the elutchwill actuate the pinion which, by means of the idler, will cause the rotation of the cable drum 19 for the purpose of winding thecable upon said drum.

The cranes as made now are provided with means whereby the lowering of the boom with the load suspended therefrom may be effected with the aid-of the engine of the crane for what is known as precision lowering of the boom. For that purpose additional gear wheels are used. One, a sprocket wheel 46, is mounted at one end of a hoist shaft, 101, marked in dotted lines in Fig. 2, which shaft is driven through intermediate means by the engine of the crane. The other wheel, also a sprocket wheel 47, is mounted upon a shaft 48 whichcarries 'a gear wheel 43w for engagement with. the gear wheel 20. A chain 49 serves to connect the sprocket wheels operatively to each other. A clutch 50, adapted to be operated manually by a handle 51, serves as a means of Patented, Nov. 24, 1959.

employing the power of the engine to control, through said sprocket wheels and the gear wheel 20, the rotation of said hoist drum 19.

The important consideration of the present mechanism is a that the operator intending to lower the boom with its load must remember to employ the clutch before he pulls back the hoist lever 32, or the boom, with its load, may drop down so rapidly that it may damage property and endanger the lives of persons within range of the boom. I shall now describe my improvement designed to eliminate the possibility of such a danger.

Secured to the upper portion of said lever 32 is a rod 54 which at'the opposite end is connected to an ohlong bar 57 having a shoulder 58. The other end of the bar is cut off at an angle, as shown at 59. The bar fits slidingly between two guiding plates marked 60 and 61 supported by a metal strap 62 'secured to the framework of the crane.

The clutch 50, shown in Fig. 2, is operated by a handle 51 extending radially from said clutch, while another radial member 63, in a diametrically-opposed position to ihe handle, is pivotally connected to a bracket 64 on beam Mounted on handle 51, by means of a U-shaped fork 65 extending horizontally from the handle, as shown in Figs. 6 and 9, is a roller 66, the rim of which is normally in abutment with the angularly cut-oft end 59 of bar 57. A coiled spring 67, at one end anchored to a stationary part of the frame-work of the crane, as shown at 68, is at the other end attached to the end of handle 51, as shown at 69, the spring serving to keep the clutch in its inoperative position withrespect to the hoist shaft. A wire member 70, looped upon itself in a U-turn, is at one end attached to the underside of plate 61, the looped portion serving to limit the extent of the movement of the handle 51 outwardly from its normal position.

At a point between the clutch 50 and the roller-supporting fork 65, the handle 51 is connected to one corner of a triangular plate or crank 72 pivoted at 73 upon a pin 74 secured to a stationary member 74a of the framework of the crane. Another corner of plate 72 is pivotally connected to a vertical rod 75. The rod extends downwardly and is secured to one end of the horizontally-disposed arm 76, as already described, which includes a shoulder 79 which serves as a pawl for engagement with the teeth of the ratchet wheel 30.

Another rod 80 connects the outer end of the arm 76 with one end 81 of a triangular plate 82 which is pivoted at 83 upon a stationary member 88 extending from the underside of the turntable 17. One corner portion of the plate 82 is pivotally connected to a short rod 85 which passes through an opening in the upright portion of an L-shaped bar 86, as shown in Fig. 2 the short rod terminating with a knob 87. The horizontal portion of the L- shaped bar is supported by the bell crank 38, as best shown in Fig. 11.

To complete the description of my device, I first wish to refer to Figs. 3 to which show the lever 32. The lever includes a vertical rod 90 which in its upper portion is axially disposed within the handle 92 of said lever and terminates with a knob or button 93 projecting above the top of said handle. At the lower end the handle includes a laterally-turned portion 94. A spring 95, coiled about the rod, bears at the top against a disk 96 which is secured to the rod, while the lower end of the spring is based within the lower portion of the handle. The rod passes downwardly from the handle through an aperture 97 therein, and includes, at its lower end, a radiallyturned short finger or lug 98 which normally fits into a recess or notch 99 in an arcuate portion 100 in bracket 34.

As long as the lug fits into the notch, the lever 32 will be locked in position. To employ the lever to actuate the boom, the operator must depress the button 93 to disengage the lug from the notch. This is a well-known mechanism and needs no further explanation.

In order to describe the operation of my device, it will be assumed that the boom is in its raised position and that lever 32 is locked against operation by means of said lug 98, as above stated.

Assuming now that the boom is to be lowered under the control of the engine of the crane, the lever 32 is pulled by the operator rearwardly, that is, in the direction of said operator, as is the case in the present practlce. For this purpose the knob 93 at the top of the handle 92 has to be depressed to disengage said lug 98 from the notch 99. As the handle is swung towards the operator, bar 57, which is located at the top member 56 and which is connected to the handle by means of rod 54, will be pushed against the roller 66, best shown in Figs. 6 and 7. The roller, as stated above, is mounted on handle 51 which radially projects from the clutch 50.

Under the present practice the clutch has to be operated manually. When the operator wants to lower the boom under the power of the engine, he has to pull the handle 51 towards himself or at right angle to the plane of movement of the lever 32. It is by means of said clutch, applicable to the hoist shaft of the crane, that the engine may be coupled to the hoist drum 19. The sliding bar 57 eliminates the need of operating the clutch manually, as by a wedge action against the roller it moves handle 51 secured to said clutch from its position as shown in Fig. 6 to the position shown in Fig. 7, in which position the clutch will couple the engine to the cable drum. I

Simultaneously, as a result of the said pull upon the lever 32, two other functions are performed: Brought to the position shown in Fig. 7, the handle 51 will tilt the pivoted triangular plate 72, causing rod 75 to depress one end of arm 76. As the arm includes a shoulder 79 which serves as a pawl for engagement with the teeth of the ratchet wheel 30, the depression of the arm will move said shoulder out of engagement with said wheel, permitting the ratchet wheel to rotate together with the brake wheel 24.

At the same time, the lower end of the lever 32, below the pivoted mounting of the lever at 33,- will operate the bell crank 38 which carries the brake-release lever 39.

As stated above, it is a coiled spring 29 that serves to keep the brake band in a tight frictional contact with the rim of the brake wheel 24, the spring being coiled about a rod 28. As one arm of the bell crank 38 is pulled by rod 36, the lever 39 carried by the other arm of the crank moves the rod longitudinally in the direction of the brake wheel against the tension of the spring and loosens the hold of the brake band upon said. brake wheel 24.

As so operated by the same bell crank 38, the vertical lever 42 will move the clutch 45 to its inactive position. Normally, the clutch serves to actuate a pinion which, through the idler 22, engages the gear wheel 20 on the hoist drum for the purpose of raising the boom. As the boom is to be lowered, the clutch is withdrawn to its inoperative position with respect to said pinion. The loosening of the brake band 25 and the shift of the clutch into its inoperative position will couple the gear wheel 20 to the hoist shaft by means of the sprocket wheels 46 and 47. As the hoist shaft is driven by the engine of the crane and as the engine is capable of a wide variety of speeds, the rotation of the cable drum rotating with the gear wheel 20 may be retarded as de sired. Thus, the boom, even when carrying heavy loads, may be lowered slowly and safely and with precision.

When the load has been lowered and allowed to rest upon a suitable support or removed from means by which it was carried when suspended on the cable, the lever 32 controlling the raising and the lowering of the boom may be pushed forward to its initial position from which it had been pulled back for the purpose of lowering the boom. As a result thereof, the bar 57 will be retracted till its angularly cut-off end 59 will permit the spring 67 to pull the handle 51 from its position shown in Fig. 7 to its initial position shown in Fig. 6 As the handle is operatively connected to the clutch 50, the return of the handle to its initial position will result in uncoupling of the hoist shaft of the crane, through intermediate gear means, from the cable drum 19.

Simultaneously, the movement of the handle to its initial position will actuate the triangular plate 72 and the rod 75 suspended therefrom, and will raise the horizontal bar 76 for engagement with the teeth of the ratchet wheel 30 by means of the shoulder 79 on said bar.

In addition, the forward movement of the lever 32 will effect a tightening of the brake band 25 upon the wheel 24. This will be effected by means of the link 36 acting upon the bell crank 38 which, in turn, is operatively connected to the spring 29 normally serving to tighten the brake band upon said wheel 24, as described in the course of this specification.

The above movement of the link 36 and of the bell crank 38 will also actuate lever 42 to bring clutch 45 to its normal operative relation to the swing shaft, whereby the shaft will be coupled to the cable drum for the purpose of raising the boom.

Upon having described my device and the manner of its operation, I want to present the following claim:

In a crane including a boom and a drum for a cable to support the boom, in combination a power-driven hoist shaft, a train of gears connecting the hoist shaft to the cable drum, a clutch vupon the hoist shaft to couple the hoist shaft to the cable drum to lower the boom, a radial handle secured to the clutch and pivotally connected at one end to a stationary support, spring means acting upon said handle to keep the clutch in a normally inoperative position, a power-driven swing shaft, a clutch upon said swing shaft to couple it to the cable drum to raise the boom, the clutch being normally in its operative position, a manually-operated lever remote from both clutches, a rod connected to the lever for the operation of the clutch upon the swing shaft, and a horizontal rod at one end connected to the lever and terminating at the other end with a bar which, on the movement of the lever to uncouple the swing shaft from the cable drum will be actuated by the lever to bear against the handle to shift the clutch upon the hoist shaft to its operative position.

References Cited in the file of this patent UNITED STATES PATENTS 1,469,579 Borden Oct. 2, 1923 1,470,321 Cooper Oct. 9, 1923 1,579,903 Yungling Apr. 6, 1926 2,445,116 Hus-ton July 13, 1948 2,501,198 Wagner et a1 Mar. 21, 1950 2,681,205 Bannister et a1 June 15, 1954 

